Built for active composters

Plan the pile, size the application, prove the payoff.

Use free compost calculators to balance greens and browns, fix pile moisture, size raised bed compost, plan lawn topdressing, and estimate compost value with research-backed formulas.

Browse all 10 calculators Inspect sources and formulas
Balance a new pile Blend greens and browns before you build. Fill a raised bed Convert dimensions into compost volume and bag counts. Measure climate impact See the landfill-diversion payoff in CO2e.
Catalog size 10 tools

Coverage for pile building, amendment planning, and impact tracking.

Unit support US + metric

Every calculator works in both systems and keeps the preference across visits.

Source base USDA + extension

Thresholds and formulas are traceable to field guides, not anonymous forum lore.

Workflow Fast inputs

Built for quick decisions when you are standing in the yard, shed, or greenhouse.

Choose the job

Start from the problem you are solving.

Build and troubleshoot the pile

Use this path when you need to balance feedstocks, fix moisture, or understand whether the pile is heating the way it should.

 Figure out how much compost to apply

Use this path when you are filling raised beds, topdressing a lawn, improving a garden bed, or mixing compost into containers.

 Quantify value, savings, and worm systems

Use this path when you want to estimate compost value, calculate carbon savings, or size a worm bin that keeps up with food scraps.

Mix and pile management

Balance your compost recipe, correct pile moisture, and track compost temperature before a slow, wet, or smelly pile turns into a bigger problem.

Most useful on day one

Amendment and application planning

Calculate how much compost to add to a raised bed, lawn, garden bed, or container mix so you buy the right amount and apply a safer depth.

Where most finished compost gets used

Value, impact, and indoor systems

Measure compost value, estimate carbon savings, and size a worm composting system when you need numbers for budgeting, reporting, or home setup planning.

Useful for reporting and planning
Why trust this

Science-backed compost calculators for piles, beds, lawns, and worm bins.

Use these compost tools to calculate carbon to nitrogen ratio, compost moisture, raised bed volume, lawn topdressing depth, garden bed amendment rates, container mix percentages, compost value, and CO2 savings without guessing.

The formulas come from source-traceable references including NRAES-54, USDA and EPA references, and extension programs from Cornell, Penn State, NC State, Oregon State, and other land-grant schools.

What gardeners need most
  • Fast compost ratio and moisture checks before the pile stalls.
  • Raised bed, lawn, and garden volume math that converts directly to bags or cubic yards.
  • Clear compost temperature, moisture, and application targets instead of vague advice.
Sources and formulas

See the full methodology and citation list for compost formulas, recommended ranges, and source notes.

All calculators use data from USDA, university extension services, and the US Composting Council's CREF feedstock database. Where sources disagree, we show both values. See our full methodology and citations.
Common questions

Frequently Asked Questions

Short answers for the thresholds and application rates people ask about most often before they open a calculator.

What is the ideal carbon-to-nitrogen ratio for composting?

The ideal starting C:N ratio is 25:1 to 35:1, with 30:1 most commonly cited as optimal by extension services including Cornell and NC State Extension. Piles in this range decompose actively and heat up reliably. Below 20:1, excess nitrogen volatilizes as ammonia — causing odor and nutrient loss. Above 40:1, decomposition slows because microbes exhaust their nitrogen supply. Use the C:N Ratio Calculator to blend "greens" (grass clippings, food scraps, manure) with "browns" (dry leaves, straw, cardboard) to hit your target.

How hot should a compost pile get?

Active thermophilic composting runs 131–160°F. The EPA's PFRP standard requires temperatures above 131°F for several days to kill weed seeds and human pathogens. Temperatures above 160°F can kill the beneficial microbes doing the work — turn the pile or add water if it exceeds this. Below 105°F the pile is in the mesophilic phase: slower, but still decomposing. The Pile Temperature Tracker classifies your pile's phase and recommends corrective actions based on current conditions.

How do I know if my compost pile is too wet or too dry?

The squeeze test: grab a handful of compost and squeeze firmly. A pile at ideal moisture (50–60% by wet weight) will hold together and release only a drop or two of water — like a wrung-out sponge. If water streams freely, the pile is above 65% moisture and may go anaerobic (producing odor). If it crumbles and falls apart without releasing any water, it's below 40% moisture and decomposition has stalled. The Moisture Calculator has an interactive squeeze-test guide, an oven-dry calculator for precise measurement, and a water-to-add calculator for dry piles.

How much compost does a raised bed need?

For a new raised bed, a mix of 30–50% compost blended with topsoil and other amendments is typical. For an annual top-dress on an established bed, 1–2 inches of compost tilled or worked into the top 6 inches is the standard recommendation from most extension services. For soil remediation of compacted or poor soil, up to 4 inches incorporated 8–12 inches deep. Enter your bed dimensions into the Raised Bed Calculator and it outputs cubic feet, cubic yards, liters and the number of bags you need to buy.

What is the carbon-to-nitrogen ratio of common composting materials?

C:N ratios vary widely. High-nitrogen "greens": fresh grass clippings (15–20:1), vegetable scraps (12–20:1), coffee grounds (20:1), chicken manure (7–15:1), blood meal (3:1). High-carbon "browns": dry autumn leaves (40–80:1), straw (75–100:1), cardboard (200–500:1), wood chips (200–750:1), sawdust (200–750:1). A balanced pile typically uses a 3:1 volume ratio of browns to greens, but the exact ratio depends on the specific materials. The C:N Ratio Calculator uses per-material density and moisture data from NRAES-54 and CREF for accurate results across 45+ feedstocks.

How much compost should I apply to a lawn?

Penn State Extension recommends ¼ to ½ inch of finished compost for routine lawn topdressing, applied with a spreader and raked to fill in thatch. More than ½ inch can smother grass, especially in a single application. For overseeding, ¼ inch provides a seedbed without burying seed. Damaged or patchy areas can tolerate up to ½ inch. The Lawn Topdressing Calculator calculates cubic yards and bags for any area, includes seasonal timing guidance by grass type, and warns you if you enter a depth that exceeds the safe threshold.

Is home compost worth anything financially?

Yes. A cubic yard of finished compost retails for $35–80 depending on location and type. Beyond replacement cost, compost delivers plant-available nitrogen, phosphorus, and potassium. Using Oregon State University's PAN guidance, the first-year plant-available nitrogen in a typical mature compost (1–1.5% total N, 10–20% first-year availability) is worth $0.50–1.50 per cubic foot in fertilizer savings alone. The Compost Value Calculator calculates retail value, fertilizer value, and combined savings for your specific volume of compost.